In children with a symptomatic viral infection (with or without a bacterial infection), the median (IQR) blood MxA level was higher (614 [209 to 1,090] μg/L) in those<2 years of age (n = 50) compared to older children (403 [170 to 716], n = 92; P = 0.045). The gene discussed is MX1; the disease is viral infectious disease.